1. Field of Invention
The invention relates to a printhead of an ink-jet printer that ejects ink droplets to a print medium to form an image thereon and also relates to a method of manufacturing the printhead.
2. Description of Related Art
A printhead of an ink-jet printer typically includes a head unit fixed to a main frame of the printhead. The head unit has a plurality of nozzles from which ink is ejected to a print medium, pressure chambers each provided for a corresponding one of the nozzles, a common ink chamber that distributes ink to the ink chambers, an actuator that selectively applies ejection energy to the ink in the pressure chambers, and an ink supply port connected to the common ink chamber. The ink supply port is connected to an ink source provided at the main frame so that ink is supplied from the ink source to the head unit.
The ink supply port of the head unit is conventionally connected to the ink source through a structure shown in FIG. 17. As shown in FIG. 17, a main frame 68 to which a head unit 6 is fixed is formed with an ink supply passage 4. The ink supply passage 4 communicates, at its upper end, with an ink source in an ink cartridge (not shown), and is open, at its lower end, toward the lower surface of a bottom plate 5 of the main frame 68. The head unit 6 is fixed to the lower surface of the bottom plate 5 using an adhesive such that ink ejecting nozzles 15 face downward and ink supply ports 19, 19 face upward.
A joint member 47 made of an elastic material, such as rubber, is interposed between the main frame 68 and the head unit 6 to connect the ink supply passage 4 of the main frame 68 and the ink supply ports 19, 19 of the head unit 6. The joint member 47 is cylindrical and connected internally, at its one end, to the ink supply passage 4 and, at its other end, to the ink supply ports 19, 19.
The head unit 6 is mounted on the main frame 68 by compressing the interposed joint member 47 vertically to some extent and by bonding the head unit 6 to the main frame 68 using an adhesive while keeping the joint member 47 compressed. As a result, the joint member 47 has resilience and constantly presses, at its upper end, the lower surface of the bottom plate 5 of the main frame 68 and, at its lower end, the upper surface of the head unit 6. The joint member 47 seals joints between the ink supply passage 4 and the ink supply ports 19, 19 and prevent ink leakage from the joints.
In the conventional structure shown in FIG. 17, a heavy load is constantly applied from the joint member 47 to the upper surface of the head unit 6. This may cause deformation of the head unit 6 and deformation of the internal ink passages or the array of the nozzles 15, which adversely affect ink ejection and degrades print quality.
When a plurality of head units 6 are mounted side by side for color printing, even minor manufacturing errors produced in the main frame 68 and the joint member 47 may change the pressing force applied from the joint member 47 to the head units 6, causing variations in ink ejection ability of the head units 6 and deteriorating print quality. In addition, due to such manufacturing errors, defective printheads where joints between the joint member 47 and the head unit 6 are insufficiently sealed are likely to be produced, resulting in a reduction in the manufacturing yields.
As one method to increase the manufacturing yields, the head unit 6 could be connected to the main frame 68 by compressing the joint member 47 considerably. By this method, the joint member 47 makes intimate contact with the head unit 6 and seals the ink supply passage 4 and the ink supply ports 19, 19 sufficiently to compensate for the manufacturing errors of the maim frame 69 and the joint member 47. However, a heavy load constantly applied from the joint member 47 to the head unit 6 is undesirable for the above-described reasons.